This invention relates to a method for detecting whether the CPU of a "Intel 86"-family computer System is an 80386 ("386") or an 80286 ("286"). The 386 and 286 CPUs are described in detail in publications by and available from Intel Corporation, Santa Clara, Calif., including the "Intel 80386 Hardware Reference Manual," Order No. 231732-1, the "Intel 80386 Programmer's Reference Manual," Order No. 230985-1, and the "Intel 80386 System Software Writer's Guide," Order No. 231499-1, to which reference is hereby made.